The objectives are to study the role of antibodies to melanocytes in the pathogenesis of vitiligo and to determine whether the immune abnormalities present in vitiligo can be harnessed to treat melanoma. We have demonstrated that the majority of patients with vitiligo have antibodies to surface antigens on normal human melanocytes. We now wish to elucidate the role of these antibodies in the pathogenesis of vitiligo by addressing three broad questions: 1) What is the nature of the pigment cell antigens which induce immune responses to melanocytes in vitiligo, 2) Are pigment cell antibodies directly involved in the pathogenesis of vitiligo, as would be evidenced by their ability to damage pigmented cells in vitro, by a relationship between their titer and the activity of the disease, by their appearance before rather than after the onset of vitiligo, and by their ability to induce the disease in actively or passively immunized animals, 3) Are there immunological relationships between melanoma and vitiligo and can these be harnessed to treat this cancer? The results of these studies should define whether or not vitiligo is an autoimmune disease to melanocytes. If that is the case, it could lead to improved methods of treating and perhaps preventing the disease, as well as to novel methods of treating malignant melanoma.